Manufacture of printing-plates



E E. NOVOTNY.

MANUFACTURE OF PRINTING PLATES.

APPLICATION FILED AUG.6|1918.

1,377 ,5 1 6. Pa ented May 10, 1921.

fav- 7 UNITED STATES PATENT OFFICE.

EMIL E. NOVOTNY, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOB. TO J. STOGDELLSTOKES, OF MOORESTOWN, NEW JERSEY.

'MANUFACTURE OF PRINTING-PLATES.

Specification of Letters Patent.

Patented May 10, 1921.

Application filed August 6,1913. Serial No. 248,649.

T 0 (Mi w from it may concern:

Be it known that I, EMIL E. Novo'rNY, a citizen of the United States,residing at Philadelphia, in the county of Philadelphia, and State ofPennsylvania, have invented new and useful Improvements in theManufacture of Printing-Plates, of which the following is aspecification.

This invention relates to the manufacture of blanks and of printingplates composed wholly or in part of synthetic resins, such as bakelite,condensite and other phenolic condensation products.

In the manufacture of such plates as previously practised by me, a sheetof the unset or uncooked phenolic condensation product, as supplied bythe manufacturer thereof as an article of commerce has been brought intocontact with a printing plate matrix preferably having a metal face, andequipped with side bars or bearers so that when heat and pressure wasapplied with the agency of a suitable press, these bearers would limitthe closing of the press, While the phenolic material would be forcedclosely against the molding face of the matrix to reproduce thecharacters thereof as printing characters on the surface of the plate.The matrix after being cooled in the press and subsequent to the heatingoperation, and while still under pressure, has been removed from thepress and the plate then separated from the matrix. This is briefly andin a general way one procedure that I have followed in the manufactureof these phenolic printing plates. While satisfactory from a generalstand point I have found that I could im prove the process as to speed,ease of operation, less attention on the part of one who might beunskilled as a plate maker, and increase in production.

For instance in practising the general method of making a plate aboveoutlined, certain factors are liable to be encountered which willinterfere with the production of these plates on a very large scale orwhich might cause delay in some instances when the plates are made by anunskilled plate maker. For example where a plurality of plates, sayeight or ten, are to be cast in a single operation in a relatively largecasting box, and which plates might have different dimensions andthicknesses, it has been nec essary to employ side bars or bearers foreach plate, depending upon the dimensions of the plate both as tosizeand thickness. Frequently, especially in a small shop, these bearersof a requisite size might not be immediately available and time is lostin making the same. Furthermore if these bearers be not employed, butlarge sheets of the uncooked material be imposed so as to cover aplurality of matrices in the box, such plates would of course have to becut or severed subsequent to the molding operation. Under theseconditions not only would there be a loss of an amount of the platemaking phenolic material which would lie in the empty spaces between thematrices, but the cutting operation, owing to the overflow of thismaterial at the edges of the matrix would be a difficult matter from thestandpoint of separation of the material from the parts to which itadheres.

Another point is that as this uncooked plate making material is suppliedby the manufacturer thereof it has incorporated therein a certain amountof a phenolic substance which assumes a juicy, tacky, sticky state underthe application of the heat of the press in the plate molding operation.Vhile under the action of the hot press platens this sticky substancecomes to the surface of the platen or phenolic sheet and when heated andhardened provides a polished surface which is very advantageous anduseful in giving nonporous, perfect ink holding surfaces, yet at thetime of making the plate it is liable to adhere both to the surface ofthe matrix. if there be any out or imperfection in the face of thematrix, and also to adhere to the press platen or casting box sometimes,though not frequently, marring or damaging the back of the product.Furthermore in making these molded plates under the old process I havefound it, desirable to employ a matrix having a metallic molding facebecause there is a possibility that the softened and heated phenolicmaterial would stick to the surfaces against which it contacts were sucha metallic faced matrix not employed.

lVith my present invention I have eliminated these disadvantages fromthe standpoint of the manufacture of molded phenolic plates on a largecommercial scale for I so preliminarily prepare the sheet of uncookedphenolic material that not only may I dispense with the use of side barsor bearers in conjunction with the matrix or matrices in the castingbox, but I obviate the overflow of the material over the sides of thematrix at the time the plates are being made, and I also avoid waste ofmaterial by having it fiow into empty spaces between the matrices wherea number are used for a single casting operation. In addition to theelimination of these disadvantages I am enabled to gage accurately thesize or amount of material which a specific plate may require for itsmanufacture and therefore am able to cut a determined amount of materialfrom the large sheet, thereby avoiding the necessity of using a surplusamount of material, which would result in wastage. I also take advantageof the polished surface which a plate of this phenolic material willtake under heat and pressure as above stated, to obtain a nonporous inkholding surface, and such a polished surface will enable me, if I sodesire, to dispense with the use of a metallic faced matrix because theblank prepared in accordance with my invention will not stick to thematrix, metallic faced or otherwise. If desired the matrix itself may bemade with the blank prepared in accordance with my invention and ashereinafter described.

Before entering into a detailed description of my present invention Iwill briefly state that I first prepare a blank of a phenolic materialby taking a sheet of the same just as it is supplied by the manufacturerthereof, that is in its uncooked or unset condition, and I place thissheet between the fiat level platens of a heated casting box and subjectthe same to a relatively low degree of heat, say 212 degrees F. forabout one minute. This will result in the liquid-like phenolic materialof the blank oozing to the surfaces and of hardening and setting to acertain degree, and at the same time forming a highly polished surfacecoating or skin on the blank. The interior of the blank remainsrelatively soft, as this material is not a good conductor of heat. Inother words the blank is but partially cooked, being harder at the outersurfaces where it is exposed to the heat than at the interior thereofand furthermore such blank is but partially compressed, as the pressureexerted in the casting box is relatively low. The blank in thiscondition is removed from the casting box when cool. It may then beplaced in storage, and supplied to the plate maker in this form. Theblank is easily cut with a knife or machine and the plate maker may cutthe blank the desired size and proceed with the making of the plate ashereinafter described.

Referring now to the accompanying drawings in detail:

Figure 1 is a view showing conventionally the top and bottom platens ofa casting box and showing an uncooked blank ready to be partially heatedor cooked to provide the polished surface,

Fig. 2 is a cross sectional view of the blank.

Fig. 3 is a View showing conventionally the two platens of the coldpress and illustrating the plate being made against the matrix from mypreliminarily prepared blank.

Fig. at is a cross sectional view showing a modified form of plateblank, in this case a blank being composed of an interior layer offibrous material, and exterior layers of synthetic resin.

Fig. 5 is a view and end elevation of the finished plate.

heferring now to the accompanying drawings in detail, particularly toFig. 1 thereof: The letters A and B indicate respectively the upper andlower platens of a casting box. On the lower platen I mount a pressureplate C provided with side pressure bars or bearers D, and I impose uponthe pressure plate G a relatively large sheet of the uncooked phenolicmaterial just as it is supplied by the manufacturer, this sheet beingshown at E. A second pressure plate F is then placed upon the uppersurface of this sheet of material, the pressure plates being ofsufiieient size to accommodate the large sheet which is to besubsequently out up into smaller sections. The casting box is thenclosed pressure applied in conjunction with heat at a temperature ofabout 212 degrees F. For heating purposes the platens are equipped withsteam inlet pipes 1 and steam outlet pipes 2 as usual. But a relativelylow pressure is employed, and the temperature .212 degrees F. for theheat may also be considered as a low temperature in operating upon thismaterial. The heat and pressure is maintained for about one minute andduring the application thereof the li uid-like phenolic material in theblank F will ooze to the surface of the blank and be cooked or hardened,but not to its absolute final hard and set form, but just sufficient toform a relatively hard non-flowing polished skin exterior of the blankthe interior of the blank remaining comparatively soft. Water is nowadmitted to the press passing through the pipes 1 and 2, and after theblank is cooled it is removed from the press, and appears in crosssection as indicated in Fig. 2. The blank may now be stored, to besupplied to the plate maker as desired and can be maintainedindefinitely in its semi-hardened or semi-cooked condition. When it isdesired to make a printing plate, a suitable matrix shown at G is placedupon the pressure plate H having a level fiat surface. A section of apartially cooked oily polished plat is shown in Fig. 2, of sufiicientsize to cover the molding face of the matrix, or such part thereof as itmay be desired to reproduce, is then cut from the plate E, the materialbeing in such a condition that this may be done with accuracy and easeby a knife or other cutting instrument. The cut off section which isshown at I in Fig. 3 is placed in face contact with the matrix and thepressure plate H, the matrix G and the plate blank I thus assembled areplaced upon a suitable steam table (not shown) where they are subject toa heat of about 300 degrees F., which causes the blank to soften orbecome pliable, but not to flow, it possessing a pliability somewhatresembling that of leather. After so heating the assembled parts theyare, while heated, placed in a cold press as shown in Fig. 3 and the topplaten J and the bottom platen K of the press are closed and sufficientpressure exerted to compress the plate blank and to force it against themolding face of the matrix so as to reproduce in the contacting face ofthe plate blank printing characters R complemental to those characterson the matrix. No side bearers are required for this operation of makingthe plate as the material will not flow or spread, and at the same timeowing to its highly polished surfaces it will not stick either to thematrix or to the contacting parts of the press, but the type or printingsurface produced on the plate will be highly polished and capable ofreadily holding and distributing the ink during the printing operation.I have found there will be just about sufficient heat retained in thepressure plate H to set the printing plate during the pressingoperation. It will be noted that this operation of making a platepartakes more in the nature of a stamping operation than of a truemolding procedure. If desired the matrix G instead of being faced withmetal, may be made from a blank of synthetic resinous material, or sucha blank as is illustrated in Fig. 2 and is made by my method, as thepolished surface or skin will prevent the adherence of the free phenolicmaterial or varnish or even the printing plate being made directly fromthe uncooked commercial form of the phenolic material ascontradistinguished from the partially cooked blank such as I haveherein described.

In Fig. 4 I have shown a slightly modified form of printing plate blankin this case employing an intermediate layer or sheet L composed of chipboard or other fibrous material and which is provided with suitablyspaced perforations M. In making this blank two sections of the uncookedphenolic material are placed one at each side of the fibrous sheet andheat and pressure under about 212 degrees applied in the mannerdescribed for the preparation of the blank shown in Fig. 2, so that atthe completion of the blank forming operation the fibrous sheet will beembedded between the polished top layer N and the polished bottom layer0, vith the intermediate, relatively soft portions of the phenolicmaterial projecting in stud like formation through the openings orperforations in the fibrous sheet as shown at to unite the topandahottomlayersof the blank to eachother and also the fibrous sheet ina staple, homogeneous massi fTh'is blank may then beused for making-aprinting plate in precisely the same .nrauneu described for the blank'shownin Fig: '12.

My improved method of producingplate blanks and printing platesinsuresth'erewill be no hollow spots in half-tones. that the type willbe sharp and square cut and that there will be no defects throughout theprinting plate caused by the structure of the blank, as my plate blankwhen made as above described possesses a known and de terminedcompression uniform throughoutits entire structure.

lVhile I have herein shown and described certain preferred embodimentsof my invention I wish it to be understood that I do not confine myselfto all the details herein set forth by way of illustration. asmodification and variation may be made without departing from the spiritof the invention or exceeding the scope of the appended claims.

hat I claim is:

1. The herein described method of making a printing plate whichcomprises preliminarily heating and pressing a blank of synthetic resinmaterial between flat surfaces to form a relatively hard skin exteriorlyof the blank, the interior remaining relatively soft, then cooling theblank then subsequently placing the same in contact with the moldingface of the printing plate matrix and heating both the blank and matrix,then subjecting the said blank and matrix to pressure to produce in oneface of the blank printing characters complemental to those of thematrix.

2. The herein described method of making a printing plate whichcomprises preliminarily heating and pressing a blank of synthetic resinmaterial between fiat surfaces to form a relatively hard polished skinexteriorly thereof. the interior of the blank being relatively soft.then cooling the blank, then subsequently placing said blank in contactwith the molding face of the printing plate matrix and heating both theblank and the matrix at a higher temperature than employed for thepreliminary heat and then subjecting said blank and matrix to pressureto produce in one of the faces of the sheet printing characterscomplemental to those of the matrix.

3. The herein described method of making a: printing plate whichcomprises preliminarily heating and pressing a blank of phenoliccondensation product between flat surfaces at a comparatively lowtemperature to form a relatively hard skin exteriorly thereof and tomaintain the interior of the blank in a relatively soft condition andthen cooling said blank then subsequently placing said blank in contactwith the molding face of the printing plate matrix and heat.- ing boththe blank and matrix at a relatively high temperature to render theblank pliable; then subjecting said blank and matrix to pressure in acold press to provide in one of the faces of the blank printingcharacters complemental to those of the matrix.

a. The herein described method of making a printing plate whichcomprises preliminarily heating a blank of phenolic condensation productat a temperature of less than 212 degrees F, to form a relatively hardpolished skin exteriorly of the blank, the interior of such a blankbeing maintained in a relatively soft condition, then cooling saidblank, then subsequently replacing said blank in contact with themolding face of the printing plate matrix and heating the same at atemperature exceeding 2 250 degrees F., then subjecting said blank andmatrix to pressure in a cold press to produce in one face of the blankprinting characters complemental to those of the matrix.

EMIL E. NOVOT NY.

